In modern hip reconstruction surgery, there is the necessity for preparing the femur for acceptance of a prosthesis. In the past, this has been accomplished in several ways including the removal of the head and a part of the neck of a femur using a conventional surgical saw, after which the exposed surfaces of the antero-medial aspect of the femur were dressed more precisely so as to properly engage a collar that typically extended about the upper part of the prosthesis. For details relating to the preparation of femurs and the installation of prostheses, reference is hereby made to the following U.S. Pat. No. 4,357,716 entitled "Device and Method for Cementing a Hip Prosthesis in a Femoral Canal", U.S. Pat. No. 4,718,909 entitled "Method and Apparatus for Cementing a Femoral Stem Prosthesis Within a Femoral Canal", U.S. Pat. No. 4,834,080 entitled "Drill Bit Guide", U.S. Pat. No. 5,037,425 entitled "Device and Method for Cementing a Hip Prosthesis in a Femoral Canal", and U.S. Pat. No. 5,047,061 entitled "Prosthesis Holder", the disclosures of which are hereby incorporated by reference.
One proposal of the prior art for accomplishing the more precise dressing of the antero-medial aspect of the femur involves the use of a circular cutter which is rotated about a spindle that is temporarily disposed in the desired position adjacent the exposed surfaces of the femur. However, the utilization of such prior art cutters has occasioned certain disadvantages. Thus, for example, if the diameter of the circular cutter is made sufficiently large to contact the entire work surface, it extends beyond the sides of the femur and undesirably engages adjoining tissue, thus causing undesired injury and trauma. On the other hand, if the diameter of the circular cutter is made sufficiently small so as to be limited to engagement with the work surface of the femur, it does not extend over the entire work surface.
Presently when a prosthetic stem is installed in a femoral canal, be it without cement or with cement, but without sustained pressure of the cement, the shaping and cutting of the proximal end of the femur is far less critical than when the cement is pressurized and the pressure sustained until the cement is mature. Presently with power saws which have attachments for cutting at various angles, the bone is usually cut and trimmed by "eye-balling". Such trimming is dependent upon the surgeon's skill of making an acceptable cut. In some instances the surgeon may elect to employ a single circular cutter which is positional on a single spindle mounted on a trial-like femoral stem.
U.S. Pat. Nos. 4,357,716; 4,718,909; 4,834,080; 5,037,425 and 5,047,061 relate to methods and apparatus for positioning the femoral stem prosthesis and pressurizing the bone cement in the femoral canal after the femur has been inserted and accurately positioned in the canal; and pressure is maintained until the cement has sufficiently set to maintain the prosthesis in place. In order to maintain pressure on the cement and stem, a seal must be developed at the cut surfaces of the proximal femur with a sealing mechanism. It is apparent that the cut surfaces must mate accurately with the sealing mechanism. And so, after the head and part of the neck have been removed, the surgeon employs a circular cutter to cut and define a portion of the antero-medial aspect of the femur and then attempts to evenly rasp the remaining portion of the horizontal cut with that of the antero-medial surface. Lastly, the surgeon defines the slope of the posterior cut with a rasp. The two cut planes must match the two planes of the sealing mechanism. The process of matching the cut surface of the bone with the sealing mechanism entails repeated trial raspings and is time consuming, and requires a great deal of accuracy. Also there exists the possibility of removing an excess amount of cortex in a given area, and so the method of employing sustained pressure after the stem has been inserted into the canal is abandoned and the stem is inserted into the cement without sustained pressure. This is unsatisfactory.